Tiania



UNITED STATES PATENT OFFICE.

MATHIAS SEM, OF CHRISTIAN IA, NORWAY, ASSIG-NOR T DET NORSKER AKTIESELSKAB FOR ELEKTROKEMISK INDUSTRI, NORSK INDUSTRI-HYPOTEKBAN K, 0]? CHRIS- TIAN IA, NORWAY.

PROCESS OF TREATING SULFII) ORES.

No Drawing.

To all whom it may concern:

Be it known that I, MATHIAS SEM, a suband exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to a treatment of sulfid ores and has for its object an improved process for the recovery of the valuable constituents contained therein.

Large deposits of lowgrade iron pyrites occur, which owing to the presence of considerable quantities of impurities (principally quartz) cannot be profitably utilized according to known methods.

Various investigators have tried to smelt such pyrites in electrical furnaces and as a result have obtained a separation of slag and matte, and a distillation of about foursevenths of the pyritie sulfur (the free sulfurg, The matte thus obtained consists of Fe CuS, etc.; and the valuable constituents of the pyrites, viz., Cu and the like, are increased in quantity in proportion to the gangue se arated and the quantity of sulfur'expelle The concentration of copper, etc., obtained by such a process is, however, in most cases insuflicient to permit its recovery from the resulting matte by means of smelting operations. To recover the copper it would in most cases be necessary to allow the sulfid melt to become hard, to remove the residue of the sulfur from the hardened melt by roasting, and to subject the roasted procluct to a subsequent process.

I have found, however, that such a process is not practical, and that the recovery of the principal part of the sulfur and a further concentration of the copper in the matte should be effected in a single process. How this result may be obtained will be understood from the following theoretical considerations regarding the conditions of desulfurization,

Specification of Letters Patent.

Patented Sept. 30, 1919.

Application filed .lune 15, 1916. Serial No. 103,792.

As is known the liberation of sulfur, wluch may be represented by the equation FeS =FeS+S,

does not come to a stop at the FeS stage, as the latter substance is, at a sufficiently high temperature, decomposed according to the equation FeS=Fe+S.

The metallic iron thus formed separates out in the matte.

By calculation it will be found that the dissociation temperature of the sulfid of iron is about 1000 C. at atmospheric pressure. The dissociation pressure at constant temperatures is a constant, independent of the relation of the FeS in the pyrites as long as the latter is in an unmelted condition. It is therefore possible to bring about a complete desulfurization by workin at a partial pressure for the gaseous su fur lower than the dissociation pressure in the solid pyrites. However at temperatures below the melting point of the pyrites the velocity of the reaction is too slow to be practical. Therefore it is necessary to work at higher temperatures, that is to say with the pyrites in a molten state. In this case, however, a complication arises in that the dissociation pressure of the sulfur in the melt is no longer constant at constant temperatures but decreases with the liberation of sulfur. For this reason a complete desulfurization of the pyrites cannot then be brought about at any temperature. According to Juptner about 4 of the sulfur contained in ferrous sulfid, FeS, is distilled off at 1500 C.

To effect a more complete desulfurization it is necessary to lower the partial pressure of the gaseous sulfur below its dissociation pressure in the melt,

This may be effected by diluting the volatized sulfur with an indifferent gas, or by transforming the sulfur into a chemical compound which has a lower partial pressure, or if desired by a combination of these methods.

Technically the desired result may be effected by blowing over or through the melt an indifferent or chemically reacting gas (producer gas with or without the addition of air, hot combustion gases and the like), provided the temperature in the furof Fe, F eS and C11 8 Whlch is enriched 1n nace is kept sufficiently high.

The inventor has discovered that by blowing the gas over or through molten pyrites at about 1500 .C., a method of working which is possible only in modern furnaces (especially in the electric furnace), it 1s possible to effect a partial roasting of the pyrites. Under the above working conditions more iron is reduced to the metallic state than in prior processes where lower temperatures were employed; consequently the loss of sulfur in the form of SO ismuch reduced. Furthermore the following:

Thus the blast should serve a double purpose, viz:

1. To effect a further desulfurization by maintaining the partial pressure of the gaseous sulfur below its dissociation pressure in the melt;

2. To oxidize the iron and thereby permit a flowing of this metal, whereby a further decomposition of the pyrites will take place, and the matte will become more concentrated in copper.

It has been found that by combining the above mentioned features in the manner described a single process may be effected which is particularly suitable for pyrites rich in quartz and containing copper. The process may be generally characterized as embodying (1) desulfurization and the recovery of elemental sulfur; (2) a separation of slag and matte; and (3) a further concentration of copper in the matte.

The process may also be used for treating a pyrites which is' free from or poor in copper for the purpose of producing metallic iron (rich in sulfur). In this case a gas, which is wholly or partially inert is used as a blast. In any case the product obtained will differ front the generally known matte by having a marked metallic nature;

Ewample 1.

An iron pyrites containing per cent. of copper is smelted in an electric furnace, alimited quantity of a mixture of, producer gas and air being blown into the same. Sulfur distils off. The producer gas is burned forming primarily carbon dioxid (G0,) which oxidizes the iron to FeO, being itself reduced to CO. The FeO pro- FeO'+SiO :FeSiO The resulting matte consists of a mixture copper in proportion to the quantity of slag produced and to the quantity of sulfur which is distilled off.

If the pyrites does not contain a sufficient quantity of quartz this substance is added to the charge. The gas obtained is combustible and after the separation of sulfur may be used anew, for instance by working with a circulating gas.

Ewample 2.

Iron pyrites free from copper is melted I in the manner above described, a producergas free from CO being blown into the charge. Sulfur is then distilled off and a strongly metallic matte is produced, which may be used'for instance to produce technical iron, iron alloys and the like.

The degree of desulfurization depends upon the quantity of blast employed and of the temperature of the melt. The foregoing detailed description has been given for clearness of understanding and no undue limitation should be deduced therefrom but the appended claims should be construed as broadly as permissible in view of the prior art.

What I claim as new and desire to secure by Letters Patent of the United States is: l. The method of treating sulfid ores and recovering the sulfur therefrom, which comprises heating the ore in a molten condition at a temperature sufficient to effect decoinposition thereof while maintaining a de,

creased vapor pressure of the sulfur vapor by means of a gas indifi'erent to sulfur, thereby obtaining a maximum yield of sulfur and amore or less metallic matte. V

2. The method of treating sulfid ores containing iron and recovering the sulfur, which comprises heating theore in a molten condition at a temperature sufficient to decompose ferrous sulfid while maintaining a decreased vapor pressure of the sulfur vapor by means of a gas indifferent to sulfur. 3. The method of treating sulfid ores con-.

taining iron and recovering the sulfur,

which comprises heating the ore in a molten condition to a temperature sufficient to decompose ferrous sulfid While'maintaining a decreased vapor pressure of the sulfur vapor by means of a gas indifferent to sulfur i and substantially free from. carbon dioxid.

4. The method of treating sulfid ores con-' 1:25

taining iron and copperand recovering sulfur, which comprises heating the ores-in a molten condition at a temperature sufiicient to decompose ferrous sulfid (FeS) and.

treating the melt with a gas indifferent to sulfur.

5. The method of treating sulfid ores containing iron and copper and slag forming materials, which comprises heating the ore in a molten condition in the presence of a gas and at a temperature suflicient to cause a large part of the iron to enter the slag, said gas being of a composition to permit the distillation and entrainment of free sulfur, thereby obtaining a matte enriched in copper.

6. The method of treating sulfid ores containing iron, copper and slag forming materials, Which comprises treating the ore in a molten condition with a gas indifferent to sulfur and containing combined oxygen, whereby a partial oxidation of the ore is effected, iron oxid being produced, which combines with the silica and enters the slag, distilling off the free sulfur and obtaining a matte enriched in copper.

7 The method of treating sulfid ores containing combined iron, which comprises treating the ore in a molten condition at about 1500 (1, While supplying a gas capable of liberating sulfur in a free state.

8. The method of treating sulfid ores containing combined iron, which comprises sub jecting the ore in amolten condition at about 1500 C. to the action of producer gas.

In testimony that I claim the foregoing as my invention, I have signed my name in presence of two subscribing witnesses.

. MATHIAS SEM. Witnesses:

C. NORMAR, C. FABRIOIUS HANSEN. 

